Two-time World Champion Mika Hakkinen believes it is unlikely that Mercedes will be "competing too much" this season while he feels McLaren will be on "top form".
Mercedes didn't have the best of times during the first pre-season test at Jerez last week with Nico Rosberg and Lewis Hamilton completing only 29 laps between them on the opening two days due to an electrical fault and rear brake failure respectively.
Although they had more success on the final two days by completing almost 300 laps, the general consensus is they still have a long way to go before they can challenge the likes of Red Bull, Ferrari and Mclaren on a regular basis.
"With the first test you never really get a 100 per cent picture of exactly where the performance of the car is," Hakkinen told BBC Radio 5 Live.
"It's a bit too early. I believe at the next test in Barcelona (starting on February 19), that is going to be more interesting to see who is at the top of the list."
He added: "I have a strong feeling McLaren are on top form this year.
"Mercedes were not exactly up to the speed I expected them to be, so I don't see them competing too much this year."
As for the challenge that awaits Hamilton at Mercedes, Hakkinen feels the Britain will get stiff competition from his team-mate Rosberg.
"Lewis has been with McLaren for so many years and I think, for him, it was time to change," he said. "It's just a job to be honest.
"There are no emotional feelings about it, you are there to win, you are racing with the team and you do your maximum for the team. Lewis has now moved to Mercedes and that is going to be interesting because his team-mate Nico Rosberg is also a very quick driver."